#include <bits/stdc++.h>
using namespace std;


int main(int argc, char const *argv[])
{
    double x;
    cin >> x;
    
    double l = 0, r = x;
    while(r - l > 1e-8){
        double mid  = (l + r) / 2;
        if(mid * mid >= x) r = mid;
        else l = mid; 
    }    
    cout << l << endl;
    return 0;
}
